Deserialization of Untrusted Data Affecting @openzeppelin/contracts package, versions >=3.2.0 <4.4.1



    Attack Complexity Low

    Threat Intelligence

    EPSS 0.14% (48th percentile)
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5.6 medium

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  • published 15 Dec 2021
  • disclosed 14 Dec 2021
  • credit @chaitinblockchain

How to fix?

Upgrade @openzeppelin/contracts to version 4.4.1 or higher.


@openzeppelin/contracts is a library for contract development.

Affected versions of this package are vulnerable to Deserialization of Untrusted Data. It is possible for initializer() protected functions to be executed twice, if this happens in the same transaction. For this to happen, either one call has to be a subcall to the other, or both calls have to be subcalls of a common initializer() protected function. This can be particularly dangerous if the initialization is not part of the proxy construction, and reentrancy is possible by executing an external call to an untrusted address.

NOTE: This vulnerability has also been identified as: CVE-2021-46320


Serialization is a process of converting an object into a sequence of bytes which can be persisted to a disk or database or can be sent through streams. The reverse process of creating object from sequence of bytes is called deserialization. Serialization is commonly used for communication (sharing objects between multiple hosts) and persistence (store the object state in a file or a database). It is an integral part of popular protocols like Remote Method Invocation (RMI), Java Management Extension (JMX), Java Messaging System (JMS), Action Message Format (AMF), Java Server Faces (JSF) ViewState, etc.

Deserialization of untrusted data (CWE-502) is when the application deserializes untrusted data without sufficiently verifying that the resulting data will be valid, thus allowing the attacker to control the state or the flow of the execution.